Thermal behavior and failure mechanisms of lithium-ion battery under high discharging rate

High-rate discharge and overdischarge are critical stressors that accelerate thermal accumulation and structural degradation in pouch lithium‐ion batteries, yet their combined effects remain poorly understood. This study systematically investigates the thermal evolution mechanisms of pouch-type lithium-ion batteries subjected to high-rate overdischarge conditions at varying cutoff voltages and discharge rates. The research comprehensively examines both macroscopic thermal responses and microscopic structural alterations of pouch lithium-ion batteries during high-rate overdischarge events. These analyses provide an in-depth study of the thermal behavior and mechanism of lithium-ion batteries under high rate overdischarge. The results show that the temperature rise rate of 3C discharge increases and then decreases, and then increases again, which is due to the fact that the heat generation in the early stage of discharge is mainly Joule heat and polarization heat, and the heat generation of the side reaction in the late stage of discharge rises sharply and occupies the dominant position, in addition to the battery capacity slightly appears to be degraded, and 3C discharge has a greater effect on the cathode. Cathode electrolyte interphase (CEI) film formation accompanies transition metal dissolution-deposition processes, with subsequent side reaction products inducing cathode particle fracture and lattice structure destabilization. The degree of unevenness of the surface temperature of the battery is increased. Notably, copper current collector dissolution and subsequent deposition on cathode surfaces emerged under 10C discharge conditions. The batteries after 6C and 10C discharges caused irreversible damage to the structure of the battery anode and cathode materials, leading to battery failure. These findings provide critical insights for developing thermal management strategies and safety-oriented designs in high-rate lithium-ion battery systems.